3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

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3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

First of a few unrelated questions about 2 subjects relating to batteries:

1. I keep seeing these AA to D cell adapters. I've seen ones that hold 1-AA in a D adapter, and one that holds 3-AA's in a D adapter. I read a post where someone claimed there is also a 2-AA to D adapter, but after a Google search I cant find them.

Batteryjunction has the 1-AA to D, and the 3-AA to D adapters, and they have the 3-AA to D adapters running in series(4.5v) or parallel(1.5v). The questions here are: If you compared 2 identical LED flashlights, say a Fenix TK-70, with one using 4- regular alkaline D cells and the 2nd TK70 using 4 of the 3-AA adapters with 3 AA alkalines in each(in parallel), which of the 2 lights would run longer on the various brightness settings before the batteries ran dead?

Also, if you were to compare the same 2 Fenix TK-70's, but instead of using alkalines in the 3-AA adapter and alkaline D's in the other TK-70, you used NiMh AA's in 3-AA adapters in one tk-70 and NiMh D's in the other Tk-70, which light would run longer on the various brightness settings before going dead using NiMh rechargeables ?

In both comparisons above^, the batteries would be the same brand, ie. Duracell AA's in 3-AA adapters vs Duracell D's in one light, and in the other Tk-70 comparison using NiMh batteries, since Sanyo doesnt make D eneloops for whatever reason, lets say you were comparing Tenergy Centura NiMh D's in one TK-70 and Centura NiMh AA's in 3-AA to D adapters in the other TK-70.

2. Next unrelated battery question: When looking for rechargeable RCR123's for the 1st time ever last year, I initially noticed that they were 3v just like their disposable Lithium counterparts, but then I heard about 16340, which are about the same size, but they have voltages of 3.7-4.2 range. But if you put a 16340 with that higher voltage in a gadget that is made specifically for only 3v, then you may likely destroy the gadget or fry it. Then to make things even more confusing and maybe more dangerous, I took a closer look at batteries labeled as RCR123's, but noticed that many of them are 3v, others are 3.6v still others are 3.7 - 4.2v! So it seems a bit irresponsible to label different batteries with completely different voltages with the same name! Wasnt the whole point of calling these higher voltage RCR123 sized batteries by the name "16340", so that it would be obvious that these were different batteries, so that there is no confusion that may(and will) cause people to buy the wrong batteries and fry their gadgets?

Why would companies label their 3.6 - 4.2v rechargeable batteries RCR123's instead of 16340's? Why not only label the 3v Li-Ion 123's RCR123, and name the 3.7 - 4.2v batteries 16340, and be consistent in that labeling? Wouldnt that be the safer, and more responsible thing to do? I mean, when I went to buy 3.7v 14500's, I didnt see them labeled as AA's!

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

Originally Posted by HighlanderNorth

The questions here are: If you compared 2 identical LED flashlights, say a Fenix TK-70, with one using 4- regular alkaline D cells and the 2nd TK70 using 4 of the 3-AA adapters with 3 AA alkalines in each(in parallel), which of the 2 lights would run longer on the various brightness settings before the batteries ran dead?

the D cells of course they have over 4 times the capacity of a single AA alkaline

Also, if you were to compare the same 2 Fenix TK-70's, but instead of using alkalines in the 3-AA adapter and alkaline D's in the other TK-70, you used NiMh AA's in 3-AA adapters in one tk-70 and NiMh D's in the other Tk-70, which light would run longer on the various brightness settings before going dead using NiMh rechargeables ?

depends on the capacities of the nimh cells involved and their internal resistance. There are some nimh D cells that have a lot more capacity than 3AAs in parallel and some that may not have much more than that.

In both comparisons above^, the batteries would be the same brand, ie. Duracell AA's in 3-AA adapters vs Duracell D's in one light, and in the other Tk-70 comparison using NiMh batteries, since Sanyo doesnt make D eneloops for whatever reason, lets say you were comparing Tenergy Centura NiMh D's in one TK-70 and Centura NiMh AA's in 3-AA to D adapters in the other TK-70.

I don't know the capacities of those batteries just look them up and add the AAs together and compare them to the Ds.

2. Next unrelated battery question: When looking for rechargeable RCR123's for the 1st time ever last year, I initially noticed that they were 3v just like their disposable Lithium counterparts, but then I heard about 16340, which are about the same size, but they have voltages of 3.7-4.2 range. But if you put a 16340 with that higher voltage in a gadget that is made specifically for only 3v, then you may likely destroy the gadget or fry it. Then to make things even more confusing and maybe more dangerous, I took a closer look at batteries labeled as RCR123's, but noticed that many of them are 3v, others are 3.6v still others are 3.7 - 4.2v! So it seems a bit irresponsible to label different batteries with completely different voltages with the same name! Wasnt the whole point of calling these higher voltage RCR123 sized batteries by the name "16340", so that it would be obvious that these were different batteries, so that there is no confusion that may(and will) cause people to buy the wrong batteries and fry their gadgets?

labeling was done prior to all the differences existing I believe. The RCR label was used for the first lithium ion rechargable 123 sized battery even though it wasn't an exact replacement at 3.7-4.2v range the label stuck.

3. Lastly, why doesnt Sanyo make C and D Eneloops?

Thanks...... Patrick

Sanyo did make a C or D eneloop but I think it was AAAs in parallel in a battery container as a D cell? It was never offered in the US. The problem with trying to market C and D sized nimh batteries is the cost of them plus a decent charger plus taking into account fast enough charging to make them compete with AAs and lithium ion battery solutions makes for a large expense. Imagine it takes 4-5 eneloop AAs to equal a eneloop D cell that would be about $10-$20 a battery then a charger that can charge a 8000 to 10000mah battery up in decent time perhaps 4 hours would cost another $50+ now you have around $100 for 4 batteries plus charger something that cannot compete with buying 4D alkalines for $4. Someone would have to be running through a lot of batteries to make that cost of about 25 recharges works for them.

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

Just to comment on "RCR123" vs. "16340". "RCR123" is a bit of a misnomer IMO. What it suggests is a rechargeable CR123 cell, of which there is no such thing.

A CR123 cell is a lithium primary cell which contains actual lithium metal, or "metallic lithium". These cells are not rechargeable. As has come up before here on the Forum the designation, or name comes from the NiCd days. These cells were two thirds (2/3) the length of an "A" cell and approximately the same diameter (an "A" cell is actually 17mm in diameter and 50mm long, or a "17500"). Individually these cells were referred to as one (1) two thirds (2/3) A cell. In reference to lithium primary cells of this size, "CR" means the cell contains a cathode which contains metallic lithium (symbol for whatever reason is "C") and is round (R).

Nowadays the 16340 designation as well as the other numerical sizes, 14500, 18650 etc. are used primarily for designating Li-Ion cells (although not necessarily), which by the way, contain no lithium, only lithium ions in their chemical formula. In the case of a 16340 cell the cell is 16mm in diameter, 34mm long, and is round (0). Some distributors confuse the last digit when the cell is xx.5 mm long and simply use eg. 17335, meaning the cell is 33.5mm long. This is not really correct as I believe a cell ending in "5" rather than "0" means it is a prismatic (non cylindrical) cell.

Anyway, RCR123 and 16340 mean the same thing, usually a Li-Ion cell that is the same size as a 2/3 A cell. Perhaps AW has the best alternative to "RCR123", he just calls them "R123" cells, meaning a rechargeable 123 size cell, which of course, would by necessity mean a Li-Ion cell.

As for the 16340 size, in the case of Li-Ion cells, there are actually four different types with three different charging requirements. The most common is the LiCo, or lithium cobalt oxide cathode type (also called ICR or LiCoO2). These cells charge with a 4.20 Volt CV stage and have a 3.6-3.7 Volt nominal voltage under load. There are also LiMn, or lithium manganese oxide cathode types (also called IMR, or LiMn2O4). These cells are also charged with a 4.20 Volt CV, and have a similar nominal voltage.

There are also two types of "3 volt" 16340 cells. The most common nowadays is the LiFe, or lithium iron phosphate cathode type (also IFR or LiFePO4 and sometimes LFP). These cells require a 3.6 Volt CV stage and have a nominal voltage of 3.2-3.3 volts.

The second type of "3 Volt" Li-Ion cell seen in 16340 size is the traditional LiCo type cell as described above, but with two diodes installed under the positive nipple. One of these diodes causes a voltage drop when the cell is under load, providing a lower voltage closer to 3 volts, although, as with any cell, depending on the load this can vary a bit. Normally the voltage of these cells is about the same as a LiFe cell under load. The second diode is installed in the reverse direction, to allow the cell to be charged (diodes only allow current to flow in one direction). Due to the voltage drop in the charging circuit, a 4.4-4.5 Volt CV stage is required to charge these cells. Behind the diode, the cell is actually being charged with a 4.20 volt CV.

The only distributors that I am aware of that supply these LiCo type "3 Volt" cells anymore, are Tenergy and Soshine. Long ago AW offered these and not too long ago, Bateryspace under their "Powerizer" brand. I suspect both have discontinued carrying these type "3 Volt" cells due to the confusion with LiFe cells and also the danger of accidentally charging a traditional LiCo cell with a 4.4-4.5 Volt charger.

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

I know that this is a bit old but appeared as I was searching for aa to d adapters and the 2-AA to D adapter that HighlanderNorth couldn't find using google was found when I searched ebay. Just figured I would share.

"what do you think is the fastest thing in the world?" "well I think the fastest thing in the world is electricity!" "well why?" "well as soon as you flip the switch the electricity turns on the light! It's instant!" ​

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

Originally Posted by HighlanderNorth

Also, if you were to compare the same 2 Fenix TK-70's, but instead of using alkalines in the 3-AA adapter and alkaline D's in the other TK-70, you used NiMh AA's in 3-AA adapters in one tk-70 and NiMh D's in the other Tk-70, which light would run longer on the various brightness settings before going dead using NiMh rechargeables ?

A seller on eBay has this warning regarding the 3AA to D adapters he is offering: "This is a parallel battery adaptor so 3AA NIMH at 2000mah will give you a 1.2Volts D at 6000mah. ... I am currently using them on my Fenix TK70. The first three modes of the flashlight is fine, but it will NOT power the turbo mode."

EDIT: He was selling a set of 3 adapters so he was probably using the 3-battery configuration. It might work with the extension and 4 adapters using 3 NiMH each.

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

1. If you are comparing alkaline AA batteries in adaptors to alkaline D cells, it depends on how much current you are drawing. The internal resistance of an alkaline AA battery is similar to that of an alkaline D cell. So even though you have the resistance of the adaptors to consider, three alkaline AA batteries will probably have a lower resistance than one D cell. As a result, the AA batteries in adaptors will probably run longer at higher current draws. But at lower draws, the higher capacity of the D cells will win out.

With NiMH, things are somewhat different. NiMH D cells both have higher capacity AND lower resistance than adaptors containing three AA NiMH cells. So NiMH will run longer at ALL current levels.

2. As others have said, there is not just only one RCR123A. Rather, there are a few. One is the LiFePO4 RCR123A. These cells charge to 3.6V. And, like all LiFePO4 batteries, they discharge at a VERY constant 3.2V. Also, like all LiFePO4 batteries, they are safe and don't need a protection circuit (which can cause fitment issues due to lengthening the batteries and which introduce a failure point). And the 3.2V discharge is close enough to 3.0V that they can safely be used in most applications that require a 3.0V primary. Besides potential voltage issues, the only real downfall of these batteries is their rather low capacity.

The other types of RCR123A batteries use either LiCo or LiMn batteries. Like all LiCo/LiMn, both of these batteries charge to around 4.2V and discharge to 2.8V with a more or less linear voltage drop as the batteries are drained down (as opposed to the very constant voltage discharge of LiFePO4). However, LiMn is safer, has higher current capability, and generally lower capacity. In any case, the higher voltage can be a problem for devices designed around 3.0V primaries. However, some newer devices using CR123A devices are designed around a wide range of input voltages. So These batteries may not be a problem. Another potential problem is size. Because most LiCo cells are likely to be protected, the cells can end up significantly longer than a CR123A primary (or RCR123A LiFePO4 cell, which doesn't need protection).

As mentioned above, some of these higher voltage batteries use circuitry to reduce the voltage. Some batteries use a simple diode. Others can use buck circuitry in order for the battery to have a constant output voltage despite the fact that the batteries DON'T produce a constant voltage. Of course, as mentioned, some of these batteries require a special charger. And any kind of voltage reduction circuitry is a potential failure point. The circuitry can also make the battery longer, which can cause fitment problems in some devices.

3. Eneloop C and D cells were available in some markets. But they are not true C and D cells. Rather, the C cells use 4 AAA cells. And the D cells use 3 AA cells. So capacity is lower than true C and D cells - 3200mAH for C cells and 6000mAH for D cells (vs 4000mAH and 8000mAH for true LSD C and D cells).

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

I'm sorry to dig this from the ground. But I was considering buying 4 x 3 AA adapters to use in my tk70 and loading the light with 12 2500mah duracells. So each adapter is in parallel giving 7500mah. This is purely due to budget as I can get duracell nimh cheap.
Is this going to cause me any issues or danger?

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

Originally Posted by torchsarecool

I'm sorry to dig this from the ground. But I was considering buying 4 x 3 AA adapters to use in my tk70 and loading the light with 12 2500mah duracells. So each adapter is in parallel giving 7500mah. This is purely due to budget as I can get duracell nimh cheap.
Is this going to cause me any issues or danger?

The biggest concern would be of reverse charging.

I'd run the set up after a fresh charge and then measure the voltage after maybe 15 minutes of use. If any of the batteries don't fall into a window of .1 volts of the others, I'd give the idea of using the adapters up.

I've got a Sony boom box that uses 6 D cells. It sometimes sits for a couple of months at a time. I purchased the Panasonic Eneloop single AA to D units. As long as I don't use the base boost, the boom box will play all day on the six 2000 mah Eneloops.

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

Originally Posted by torchsarecool

I'm sorry to dig this from the ground. But I was considering buying 4 x 3 AA adapters to use in my tk70 and loading the light with 12 2500mah duracells. So each adapter is in parallel giving 7500mah. This is purely due to budget as I can get duracell nimh cheap.
Is this going to cause me any issues or danger?

The only issue I can think of is that there are more connections between all the batteries and thus that added resistance may limit the current draw and highest mode..............however, since this is made for alkaline D batteries, current discharge can't by higher than what you'd get from NiMh anyhow, so you're probably not handicapping it. I'm not that familiar with the TK70, but I've used aa to D adapters in other things and had pretty good luck with them. As torchsarecool mentions to have all 12 batteries at the same state of charge (in other words all of them freshly charged when you replace batteries). Each grouping of 3 batteries in the same adapter will discharge evenly and if the other adapters have the same capacity (in other words all are 2500mAh), then they most likely will also go down at the same rate as the other adapters. I think it will be obvious when you need to recharge. Some batteries will be lower than others but NiMh is pretty forgiving. If you have the batteries already, then I'd give it a try.

I have a Rayovac Sportsman Lantern that takes 3 D batteries all in series. I use the parallel 3xAA to D adapters and so I'm using 9 AA NiMh batteries. I haven't found them to vary too much from each other when I recharge. Most of the time, I'm topping them off ever before it would be obvious that they need it simply because I like to have a fully charged lantern prior to a trip.

Re: 3-AA to D adapters vs using D cell batteries? Is it an RCR123 or 16340?

Thanks for all replies. I was hoping nimh would eradicate any risk from imbalances becoming explosions. It's just a cheap way for me to get the tk70 up and running properly. Ill consider it an option and see what happens